1. Field of the Invention
This invention relates to the oligomerization of alpha-olefins, such as 1-decene, and more particularly, this invention relates to the use of a loop recycle reactor system for the continuous oligomerization process.
2. Description of the Prior Art
Olefin oligomers have been previously proposed and used as synthetic lubricants. The oligomers of alpha-olefin containing from 8 to 12 carbon atoms are generally used in the preparation of these lubricants with, more specifically, the trimer of 1-decene being most useful in preparing lubricants for use in hydraulics, transmissions, transformers and the like.
Various processes have been developed in the past for the oligomerization of such alpha-olefins to produce synthetic lubricants and like products. Among these processes are those which employ a promoted boron trifluoride catalyst for the oligomerization reaction. Until recently, all of the processes developed for the oligomerization of alpha-olefins were batch processes, utilizing a variety of chemicals to promote the boron trifluoride catalyst. Representative processes for example are described in the following United States patents:
U.S. Pat. No. 2,183,503--McAlevy PA1 U.S. Pat. No. 2,766,312--Serniuk PA1 U.S. Pat. No. 2,552,508--Peters PA1 U.S. Pat. No. 2,816,944--Muessig et al. PA1 U.S. Pat. No. 3,149,178--Hamilton et al. PA1 U.S. Pat. No. 3,382,291--Brennan PA1 U.S. Pat. No. 3,742,082--Brennan PA1 U.S. Pat. No. 3,763,244--Shubkin
While each of the processes set forth in the above patents is somewhat effective in producing the desired synthetic lubricant, with varying degrees of success, each of the processes has the disadvantage that it is batch process. More recently, continuous processes for the oligomerization of alpha-oleins have been proposed. For example, U.S. Pat. No. 4,045,507 to Barrett L. Cupples, et al, and U.S. Pat. No. 4,045,508, also to Barrett L. Cupples, et al, both of which are assigned to Gulf Research and Development Company, disclose continuous processes for the oligomerization of alpha-olefins to produce a synthetic lubricant product. The Cupples U.S. Pat. No. 4,045,507 utilizes a series of at least two flow-through tank reactors for the continuous multi-stage alpha-olefin oligomerization. In accordance with this process, the 1-olefin and catalyst are introduced into and mixed together in a tank reactor for partial oligomerization and the reaction product from this first tank reactor is directed to one or more additional tank reactors in series for completion of the oligomerization.
The Cupples U.S. Pat. No. 4,045,508 also discloses a continuous oligomerization process. The process of this U.S. Pat. No. 4,045,508, however, differs from that disclosed in the U.S. Pat. No. 4,045,507 in that the partial oligomerization product from the first tank reactor is thereafter passed through a final tube reactor in order to complete the oligomerization. The processes of both patents are said to allow continuous oligomerization and control over the trimer to tetramer ratio of the final synthetic lubricant product.
A continuous process for the oligomerization of alpha-olefins to produce a synthetic lubricant product is also disclosed in a draft report of A. Sacks of SRI entitled "Synthetic Lubricants". This draft report, a copy of which can be supplied by applicant, surveys the various processes which have been previously proposed for both batch and continuous oligomerization of alpha-olefins to produce a synthetic lubricant product. The draft report proposes a model process for the continuous oligomerization of alpha-olefins, utilizing as a basis for this model the series of tank reactors as described in the Cupples U.S. Pat. No. 4,045,507 assigned to Gulf Research and Development Company. The various prior art descriptions and other features of this draft report are incorporated herein by reference.
The use of loop recycle reactors in series for chemical conversion is also known. For example, Pearsall Chemical Corporation, the assignee herein, has issued to it U.S. Pat. No. 4,052,471 in the name of Mason P. Pearsall which describes the use of a loop recycle reactor system for chlorinating substantially linear liquid C.sub.8 to C.sub.30 hydrocarbons. The system illustrated in the Pearsall Chemical Corporation patent has been commercially utilized for the chlorination of substantially linear liquid hydrocarbons in the LaPorte, Texas plant of Pearsall Chemical Corporation. Applicant, however, is unaware of any prior suggestion of the use of a loop recycle reactor system for the oligomerization of alpha-olefins or the advantages which applicant has found to be achieved through that system.